The invention relates to a coaxial collet chuck comprising at least two, preferably three clamping jaws which can be adjusted in radial direction and can be adjusted in common together.
In optical communications transmission systems using light waveguides, the optical fibers are coupled by ultra-high-precision mechanical plug connectors so that the two signal-carrying fiber cores coaxially meet one another with a precision which is within the sub-micrometer range. Thus, the connector causes a minimum signal attenuation. Accordingly, the core must be adjusted coaxially relative to the outside diameter of a plug pin of the connector with the greatest possible precision when mounting an optical fiber in the plug pin.
Up to now, the outside diameter of the plug pin during adjustment was held in a precise position by a bushing or a prism type clamp or chuck having prism shaped jaws which establish a point contact between the jaws and the plug pin. However, the diameters of these bushings are subject to fluctuations which in turn lead to dislocations between the plug pin and the core. Additionally, a prism type clamp may provide a translational dislocation between the plug pin and the core which can be identified under given conditions. Furthermore, improper plug pin diameter measurements, undetected deviations in the roundness of the plug pins, as well as high local surface pressures produced by the clamps all provide dislocations which are virtually uncontrollable.
In mechanical plug connectors, the position of the plug pin is defined by the enveloping cylinder of the plug pin which surrounds the plug pin during plugging. For this reason, the enveloping cylinder of a plug pin should be consulted as a reference for the adjustment of the optical fibers. This means that the plug pin should be accepted in a clamp unit having as large an area as possible, whereby the movement of the clamping jaws must be absolutely uniform in order to guarantee a coaxial adjustment having sub-micrometer precision within the prescribed diameter range. However, movements having the required precision cannot be realized with traditional coaxial collet chucks.